Thermostat switch



y 31 u. E. SMITH THERMOSTAT swITcH Filed May a, 1925 2 Sheets-Sheet 1 E. E- SMITH THERMOSTAT swrrca Filed May 8, 1925 2 Sheets-Sheet 2 I INVENTOR li'a E-Smith Qw' gzmiwl ATTO R N EY Patented May 31, 1.927.

UNITED :STATES IRA EDWARD SMITH, 0F STOCKTON, CALIFORNIA.

THERMOSTAT SWITCH.

Application filed May 8, 1925.

This invention relates to improvements in electric switches of the type actuated by a movable element containing an expansible fluid sensitive to variations in temperature, and whose expansion or contraction causes the movement of such element.

The principal object of my invention is to provide a switch of this general character, of a type usable either in connection with air, or with steam and hot water, having a plurality of separate switch contacts, mounted to be actuated in common .by a single liquid containing element, and so arranged that the times of opening or closing of the contacts will be different from each other.

A further object is to provide a means for adjusting the different contacts relative to each other, so that the times between their operation may be altered at will. In other words, apart from and without interference with any of the ordinary temperature regulating means commonly provided with such instruments, and which controls the temperature at which one set of the contacts will be opened, I have arranged for enabling the other set of contacts to be adjusted so that they may be set to be opened or broken at any point in a reasonable range of differences of temperature'with respect to the temperature necessary to open the first contacts.

This arrangement enables a flexibility of the control of the mechanism controlled by the switch to suit different conditions to be had. which it is impossible to obtain with only a single set of contacts, or with a plurality of contacts so arranged that they all open simultaneously, or so that their relative times of opening are fixed and unchangeable.

Another object is to employ contacts of such a nature that a current of large amperage may bepassed through the same without danger of arcing or burning the points as they are opened or closed, and of a type which will never become corroded or pitted. or undergo any deterioration or wear regardlos of the length of service. I have particularly in mind to employ this switch in connection with my oil burner system, filed November 17th, 1924, Serial No. 750,248.

This system includes a rotary burner plate. and a motor for both feeding oil to the burner plate and for rotating the same.

Serial 'No. 28,847.

When the fire is first started, the full strength of the motor, and consequently a heavy flow of oil to the plate is desirable in order to quickly raise the temperature to the desired degree. After such degree is reached it is desirable to reduce the volume of the fire (which is governed to a certain extent by the speed of the motor) in order to maintain the temperature in that degree without actually causing the fire to go out. It is further desirable that this should be accomplished automatically and without the necessity of an attendant being on hand to control the motor.

Should the heat continue to rise in the furnace to a further degree for some reason, i

or in the room in which one of the thermostat switches is located, it is then desirableto discontinue the operation of the motor and the feeding of the oil completely, until the temperature has been restorted to a predetermined low point. With my improved type of thermostat switch I am enabled to automatically take care of all such desired features in the operation of the system.

My adjustable contacts may be set so as to open within a very close range of each other, so that very accurate control of the motor, and consequently accurate control of the heatgenerated by the burner, may be maintained. This is not of course a desirable feature but is frequently of vital importance, as for instance in connection with the heat of incubators, dehydrator-s and other plants where a great variation in temperature is aptto be disastrous.

My thermostat switch, properly adjusted for the different conditions of operations involved, may be also used, in refrigerating plants, where the maintaining of the temperature at an even low point is as important as keeping up an even high temperature is in other plants and establishments.

A further object of the invention is to produce a simple and inexpensive device and yet one which will beexceedingly effective for the purpose for which it is designed.

These. objects I accomplish by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claim.

In the drawings similar characters of reference indicate corresponding parts in the several views:

' Fig. 1 is a front view of a thermostat Oil lib v switch used for hot water or steo my arrangement of cent ic" contacts being in normal positions.

- TV 0 m, Y 2. I r 1g. 4 1S a-simiisi view, one 59b oi contacts being shown broken by expe of the Bourdon tube by a @3153. ters 8 ig. s a

stat sv h sho "enipdrature pos'm I s similar v'ew, showing o" o: e contacts broken by one e e a l hragni due to a cert; l

-- -Y n 4- is vertical section 0 1' is a perspective view of cube holding bracket cached.

Fig, 8 is a motor circuit diaphragm sh ing one arrangement of wiring in wh my switch may be interposed to con oi operation of the motor.

Referring now more particularly to the characters of reference on the drawings, to 'l, 2 and 3, the steam or hot thermostat comprises a casing l in which i mounted a common form of Bourdon tub 2 in which an expansible fluid is sealed as i customary, One end of thetube is to the casing while the other end is free,

riveted in the buck of he casing is a bracket 8 having a horizontal l the pivot and a vertical. atbelow said pivot, A link 6 is nected the arm and the ire tube, so that when tube bracket is turned on. its pivot as an axis, fhese parts are commonly employed in switches of this character and of themselves form no part of my invention.

Secured onto and depending from flange 4 is a cradle T? in which is supported a horizontal glass tube 8 whose axis 15 right an res to the pivot of the bracket A srnal quantity of mercury 9, in connection with an inert gas, is contained in. the tube which is sealed.

This mercury is free to travel from one end of the tube to the other and when one end makes electrical connection between two longitudinally disposed contact points 10 which project into the tube adjacent end. v

When the Bourdon tube 2 is cold or in a non-expanded condition, the tube 8 will then lie on a slope suflicient to cause the mercury to contact with the points 10. This slope is in that direction such that an expansion of the Bourdon tube will cause the slope to be reversed relative to a horizontal plane.

Fixed in connection with the flange i and projecting upwardly from the outer end the Clibdl 4 0 1s a snniiar ibe oi the :CtlO The degree of difference e depends on the conditions oi: i apparatus in connection the switcn is to be used,

pension of the Bourdon tube, the tube 8 will gradually move from its initial slope to a horizontal position, and then beyond such position to rest at slope the reverse that ori jnally The mercury being free to flow will oi course travel to the lov\- poii the ihe result is that said mercury will leave the contact points 10 and the latter will thereiore be disconnccted'or b1 hen and the switch opened.

e slope at which Abe 15 is set, how such that its initial slope has not con entirely eliminated when the contacts 0 broken, so that the contacts 17 still remain closedv A further expansion of the Bourdcn tube will ultimately cause a reversal of slope of the tube 15 to be had, so that the COllhfiCilS 17 will then also be broken, the contacts 10 of course remaining broken all this time.

The amount of additional expansion of the Bourdon tube (which is governed by the amount of additional heat) necessary to thus breelz the contacts 17, of course depends on the relative setting of the two tubes, which as above stated, may be adjusted to suit any conditions.

The type of switch shown in Figs. 4 to 7 is one actuated by differences in air temperature, and is placed in the room in which the air is to be maintained at a certain tempcrature.

This device comprises a back plate 20 on which, near the bottom, is mounted an expansible diaphragm 21 secured with an expansible sensitive fluid which is sealed therein, A horizontal shaft 22 extends outwardly from the plate at right angles thereto a certain distance above the diaphragm, said shaft being mounted in said back plate and in support 23 at its outer end.

T urnable on the shaft 22 is a bracket 24 having an arm 25' depending from its inner end. This arm is engaged by the upper end of a laterally yieldably connection means 1n dicated at 26, and which extends thence to the diaphragm. This arrangement, which is not novel with me, causes the bracket to be rotated on the shaft one way or the other with the vertical expanding and contracting movement of the diaphragm, while preventing any, great expansion of the diaphragm from possibly straining or breaking any parts of the structure. A manually controlled regulating structure illustrated at 27 acts on the diaphragm in the usual manner to control the amount which said diaphragm must expand before causing the switch to be opened, so that the device will function when a predetermined room temperature has been reached. This mechanism also is-not novel with me, being already in use in instruments of this general type.

My contact structure, which I incorporate in connection with these standard parts, comprises a horizontal tube 28 mounted in a cradle 29 which depends from and is rigidly fixed on the bracket 24. Contacts 30 projectinto said tube adjacent one end thereof, and are adapted to be connected by mercury 31 in said tube. This tube, when the diaphragm is in its normal unexpanded condition, is set at such a slope that the mercury then engages said contact points.

Depending from the bracket 24 in front of the tube 28 is a vertical flange 24 the shaft 22 passing therethrough. Turnablc on the shaft in front of the flange 24 and abutting thereagainst is a flange 32 formed as part of a cradle -33 which supports a tube 34 of the same nature as the tube 28. The flange 32 is provided with an arcuate slot 35 under the shaft through which projects a screw 36 mounted in the flange 24*, said screw being operable from the front of the device.

It will therefore be seen that upon loosening said screw the cradle 33 may be turned one way or the other about the shaft 22 as an axis, and the slope of the tube 34 relative to the tube 28 adjusted accordingly. When the desired setting of the tube 34 is obtained the screw 36 is tightened up, binding the cradle 33 to the bracket 24 and of course causing the respective tubes mounted on such parts to turn as a unit.

The tube 34 carries contact points 37 arranged in the same relation as in the tube 28 and at the same end, said contact points being adapted to be engaged by freely movable mercury 38 contained in said tube.

The tubes 28 and 34 are set relative to each other so that with the expansion of the diaphragm, the slope of the tube 28 will be reversed and the contacts broken before the initial slope'of the tube 34 is lessened sutiicieutly to cause the mercury to disengage the respective contacts. The functioning of this type of switch is therefore the same as that first described.

In F 8 I have shown a circuit in which the first disclosed type of thermostat is inter posed, though the latter type could be used instead of the same or in connection therewith.

I11 this circuit, 39 and 40 represent positive and negative main line wires, and 41 a motor driving an oil burner or other apparatus. A lead 42 from one of the contacts 10 leads direct to one terminal of the motor, the other terminal of which is connected to the main line 40 by a lead 43. A lead 44 from the other contact 10 is connected to the lead 42, with a resistance 45 interposed therein.

it lead 46 from one of the points 17 is connected to the positive main wire 39, while a lead 47 from the other one of said points 17 is connected to that one of the points 10 to which the resistance lead 44 is connected.

It will therefore be seen that if both sets of contacts are engaged by the mercury, a current will flow from lead 39, through lead 46, to and through contacts 17, through lead47 to and through contacts 10, through lead 42 and motor 41, to the main lead 40 through lead 43.

When contacts 10 are broken, that portion of the lead 42 adjacent its contact 10 is out of the circuit. The current will then flow from lead 39 through lead 46 to and through contacts 17, through lead 47 to that contact 10 to which it is connected, and through lead 44 and resistance 45 to the motor, causing the latter to be slowed down.

If such slowing down does not have the desired temperature reducing effect and the Bourdon tube continues to expand, the contacts 17 are finally broken, which breaks the entire circuit to the motor.

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention as defined by the appended claim.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

A thermostat switch comprising a contact structure consisting of a sustantially horizontal tube containing a conducting liquid and spaced contacts depending into the tube adj acent one anti buereof turnabie bracket second tuim is mounted anci itself turnbe is -0113 I I emenlz on "which said mountei on me first named bracket, 21101 28016 by varying ta cian l' means for maintaining the connecting; means hem en the \q bracket in any desired positicn bracket fox "tm'ning e Z reiaive to said first bracket.

names anomer c In tesimc ny whereof I afiiz: my signati' the first 115,11 .60. strum:

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